/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineEditor/Public/MoviePipelineEditorBlueprintLibrary.h
Pop a dialog box that specifies that they cannot render due to never saved map. Only shows OK button.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="Movie Render Pipeline") static void WarnUserOfUnsavedMap()